1. Field of the Invention PA1 2. Brief Description of the Prior Art
The present invention relates to improvements in vehicle bodywork construction. More particularly, the invention relates to an extruded light metal end part for connection to an open end of a hollow section, light metal longitudinal beam of a vehicle bodywork, wherein the end part includes integrally formed fastening elements for attaching additional components thereto, and wherein the fastening elements are oriented along both the transverse and longitudinal directions of the longitudinal beam.
Longitudinal beams and transverse beams are used in the supporting structure of a motor vehicle body, especially in the substructure. With the self-supporting bodies commonly used today, these beams are hollow sections that are made of at least two deep-drawn plates of metal that are welded together.
The front and rear ends of each longitudinal beam are provided with an end part which allows other components to be secured to the longitudinal beam. Such end parts are also formed as deep-drawn parts made of plate steel that are welded to the longitudinal beam part. An air scoop, a radiator, a headlight, a towing hitch and a bumper mount are among the additional components that attach to the front end of a longitudinal beam.
Steel plate shaped by a conventional deep drawing process is used to form such self-supporting steel plate automotive bodies. While the compression molding dies for shaping the plate metal are relatively expensive, they do permit a high production output, so this is an inexpensive solution for mass production.
In the case for mass production on a small scale, it is known from European Patent No.: 0.146,716B1 how to produce motor vehicle bodies for passenger vehicles which have a supporting structure made of hollow sections that are joined together by junction elements. The hollow sections are designed as extruded light metal sections (ie, aluminum alloy) and the junction elements are formed as light metal castings.
In addition to providing an inexpensive solution for smaller series production runs, such a design also yields the advantages of lower body weight and better protection against corrosion. The front end part for the automotive longitudinal beam disclosed in this patent document is designed in the manner of a junction element as a lightweight metal casting with integrated fasteners. Such a light metal casting, however, is relatively expensive due to the way it is produced and the relatively large amount of material that is required.
In accordance with another known automotive body made of extruded lightweight metal sections (Aluminum Journal, published by Aluminum-Zentrale e.V., D usseldorf, also printed in the journal Aluminum, vol. 64, no. ,9(1988)), the respective front ends of two parallel, spaced apart longitudinal beams are joined together by a transverse beam that is butt-welded in place. This published document does not teach or suggest how to attach extra parts to the longitudinal beams.
A generic end part for an automotive longitudinal beam is also disclosed in U.S. Pat. No. 4,988,230. This part document shows a longitudinal beam part that is designed as a hollow section beam and an end part that is inserted within the one end of the longitudinal beam part. The end part further includes at least one fastening element for fastening other parts. The end part is formed as an extruded section with a closed, ring-shaped outer wall.
In this example, the longitudinal axis of the end part and the longitudinal axis of the longitudinal beam part are at right angles to each other, and the length of the section of the end part corresponds to the inside diameter of the longitudinal beam part. The two opposing cut faces of the end part are in one plane and are parallel to each other. In order to achieve a form-fitting contact with the plug-in connection, the inside contour of the longitudinal beam part must be designed with two parallel flat surfaces. Thus the cross-sectional contour of the longitudinal beam hollow section cannot be designed with just any dimensions in the end area, but instead the cross sectional contour is determined essentially by the cut surfaces of the end part.
This is especially unfortunate in the case where the longitudinal beam is formed as an extruded light metal section since an extruded light metal section has a constant cross-sectional contour over its entire length due to the limitations in the extrusion process. Accordingly, for such a case, the design emphasis of the extruded light metal beam is based on the geometry of the insertable end part, rather than the more important design criteria of rigidity, deformational properties, and the impact energy absorption capability of the longitudinal beam.
Since the end part in the above example is also manufactured as an extruded section, the shape of the integrated fastening elements in the longitudinal direction is given. The bolt holes on these integrated fastening elements, especially for screw connections, therefore run in a transverse plane of the motor vehicle when used on a longitudinal beam with the known arrangement. However, other parts which are bolted onto the end of longitudinal beams, such as bumpers, use bolt fasteners which have a tightening direction that is in the longitudinal direction of the motor vehicle. Accordingly, it would be desirable to provide an extruded section end part which would permit the attachment of additional parts or components irrespective of the tightening direction of the associated fasteners.
Published Japanese Patent Document Number 4-66374A (published in: Patent Abstracts of Japan, sect. M, vol. 16 (1992), no. 270(M-1266)) discloses a known end part design for a longitudinal beam in a motor vehicle body wherein the longitudinal axis of an end part is coaligned with the longitudinal axis of the longitudinal beam onto which the end part is connected.
This document, however, does not disclose any fastening elements mounted on the end part which allow other parts to be secured thereto, nor does this document teach or suggest to form an insertion-type connection over the entire cross section of the longitudinal beam.
Accordingly, the problem on which the present invention is based is to improve the design of a generic end part for a hollow section automotive longitudinal beam to the extent that greater freedom is allowed with regard to the design and dimensions of the hollow section longitudinal beam while still achieving an inexpensive and stable design for the end part.